It's one of the great ironies of capitalism/free market economics. Economists promote the free market because competition is good, however corporations in a free market end up buying each other out because it's easier and more profitable than competing.

It is because wireless is not a free market, but a regulated one. If it was a free market, it would be possible for anyone to create a competitor and start selling services.

However, since for wireless services, the number of frequencies is limited, and government have chosen to allocate them to a specific company, the market is not free but regulated, with limited competition. Hence the opposite of what economists promote. I actually have never heard of any economists promoting such a model, having a regulated market in the hand of private companies can only lead to price agreements and lack of innovation, since it is the best way to guarantee the maximization of profits.

The alternative would have been to have a state agency build the antenna and control the frequency, and rent them to any company for the same price. However, it would not solve the problem of innovation, since such agency tends to suffer more from bureaucracy and delay in implementation. But then you would get a free market. This is basically why, many countries also force wireless companies to allow virtual operators, but since the big companies can choose the price they sell to the virtual operators, it does not end up in more competition.

"It is because wireless is not a free market, but a regulated one. If it was a free market, it would be possible for anyone to create a competitor and start selling services."

Not really, you cannot ignore that the radio spectrum gives the carriers something of a natural monopoly - and that regulation is needed to help break that up.

Under those circumstances the best you can do is rebrand someone else's service. Not sure about the rest of the world, but rebranded telco DSL was insanely popular in the US a few years back. I suppose that was a form of competition, but it was not competing networks, merely competing billing agencies.

In any case it was only because of regulation that this was possible, otherwise one corporation would own the whole network (again).